Mixing syringes having two compartments or chambers are known in the prior art. These syringes generally consist of an outer barrel with a nipple or cannula at one end, and having an open other end. An inner barrel having a dispensing end is inserted through the open end of the outer barrel and extends partially into the outer barrel. A plunger is inserted into the open other end of the inner barrel. A seal is provided at the dispensing end of the inner barrel. The seal in these prior syringes are adapted to be displaced by pressure exerted on a fluid in the inner barrel when the plunger is moved axially in the inner barrel. The seal yields to the fluid pressure and the fluid in the inner barrel flows into the outer barrel to mix with liquid, powder or solids contained in the outer barrel. After mixing is completed the inner barrel may be axially advanced in the outer barrel to cause the mixture to flow into the cannula and out of the syringe. Typical mixing syringes of the type aforedescribed are shown in U.S. Pat. Nos. 3,052,239; 3,380,451; 3,685,514; and 4,464,174.